Method for producing adhesive closure parts

ABSTRACT

The invention relates to a method for the production of adhesive closure parts, wherein a partial segment of the surface of a support element ( 1 ) is provided with adhesive closure elements ( 3 ) which stand out from the plane thereof by applying a plastic material that forms adhesive closure elements on the support element ( 1 ). The adhesive closure elements ( 3 ) are formed without any forming tools, at least in a given area, by depositing the plastic material in successively delivered droplets using at least one applicator ( 9 ).

[0001] The invention relates to a method for production of adhesive closure parts, a method in which a backing element is provided in at least one component area of its surface with adhesive closure parts, a plastic material forming the adhesive closure part being applied to the backing element.

[0002] A process of this kind is disclosed in DE 198 28 856 C1. Application of the conventional process proves to be relatively expensive especially if adhesive fastener elements are to be produced which are applied in very high packing density and are small in size. Such is the case, for example, in production of so-called microfasteners in which the adhesive fastener elements are provided in the form of stems thickened at the ends or with side projections in very high packing densities of, for example, 200 or more adhesive fastener elements per square centimeter. Form tools like dandy rollers are required for shaping the stems as desired on the end side. Very high production costs are occasioned by the very large number of sieve openings, which may be produced by etching, electroplating, or laser treatment.

[0003] On the basis of this state of the art the invention has the object of proposing a process which permits especially economical production of adhesive fastener elements with such elements tightly packed in the widest possible variety of shapes desired.

[0004] In the case of a process of the kind indicated above it is claimed for the invention that the adhesive fastener elements are formed without use of a form tool at least in one component area, in that the plastic material is deposited by means of at least one application device in the form of the finest possible droplets applied in succession and the places selected for deposit of the droplets are three-dimensional with respect to the shape of the particular adhesive fastener elements to be formed.

[0005] The structure provided for the adhesive fastener elements claimed for the invention, characterized by extremely fine droplets deposited in succession in selected places, permits formation of adhesive fastener elements of any configuration, of virtually any degree of fineness, and by achievement of the high packing densities desired without the need for correspondingly costly development of form tools. Accordingly, control of the places of droplet deposit, accomplished by appropriate relative movements of deposit device and backing element, preferably under computer control, makes possible not only formation without difficulty of the shapes indicated in DE 198 856 C1 referenced above, as stems with mushroom heads, with stellate heads, and the like, but also shapes which cannot be produced at all, or can be produced only with great difficulty, with conventional form tools, such as loops, hooks, or anchors, which can be shaped only poorly or not at all by a form tool because of the undercuts present.

[0006] By preference use is made of an application device with at least one nozzle from which the plastic material is sprayed in droplets of a size of a few picoliters. Such spray devices for centrifuging liquid plastic material may be operated by piezoelectric or electrothermal means. The plastic material consists preferably of acrylate, which sets after depositing of each droplet or group of droplets, for example, by the action of electromagnetic radiation, while the deposit site is subjected to ultraviolet radiation, or by a chemical reaction. The plastic material may, however, also be a thermoplastic set by cooling.

[0007] The adhesive fastener elements may be produced at a high speed of operation, since spray application of successive drops can be carried out at a high rate. Cycle speeds of several kilohertz may be reached immediately in computer-controlled operation. An application device having a plurality of nozzles actuated simultaneously may also be provided in order to develop a plurality of several rows of adhesive fastener elements simultaneously.

[0008] The invention is explained in detail with reference to embodiments illustrated in the drawing, in which

[0009]FIG. 1 presents a highly simplified diagrammatic perspective view of an exemplary embodiment of a device for application of the process claimed for the invention;

[0010]FIG. 2 a diagrammatic side view of the device shown in FIG. 1;

[0011]FIG. 3 an enlarged view of the area identified as A in FIG. 2;

[0012]FIG. 4 a side view of the device similar to that shown in FIG. 2, the production of looped adhesive fastener elements being shown;

[0013]FIG. 5 an enlarged view of the area identified as A in FIG. 4;

[0014]FIG. 6 a highly simplified diagrammatic side view of a device for production of adhesive fastener elements with trough-shaped heads passed through calenders; and

[0015]FIG. 7 an enlarged view of the area identified as A in FIG. 6.

[0016] FIGS. 1 to 3 serve to explain the process claimed for the invention on the basis of an example in which adhesive fastener elements with a backing element 1 in the form of a sheet of PET on the surface of which adhesive fastener elements 3 are formed, elements which have thickened areas on their ends. In the example presented in FIGS. 1 to 3, the thickened areas on the ends resemble mushrooms, as is to be seen from FIG. 3 in particular. For the sake of clarity, the adhesive fastener elements in all the figures are represented greatly exaggerated in size spaced at greatly exaggerated intervals from each other.

[0017] The backing element 1 rests on a guide roller 5 which may be driven in both directions of rotation for execution of controlled rotary steps, so that the backing element 1 may be moved back and forth in the Y axis direction within a droplet application area situated inside an application area A (refer to curved arrow 7 in FIG. 2). Droplets of liquefied plastic material are applied by means of an application device 9, which may be moved in the Z direction (see double arrow 11 in FIG. 2) and in the direction of the X axis perpendicular to the latter (see double arrow 13 in FIG. 13). Consequently, the location selected for droplet application relative to the backing element 1 may be three-dimensional; the guide roller 5, and accordingly the backing element 1, as well the application device 9, move correspondingly. As an alternative, the application device 9 could move along all three axes (X, Y, and Z) relative to the backing element 1.

[0018] The application device 9 in the example illustrated in FIGS. 1 to 3 has a nozzle 15 through which the liquefied plastic material is sprayed. In the operating situation shown in FIG. 3 the nozzle 15 assumes a position relative to the backing element 1 such that the stem of an adhesive fastener element 3 is built up by successive spraying of droplets each of a few picoliters. In the situation illustrated in FIG. 3, the stem sprayed through the nozzle 15 has been built up to about one third of its height, preferably under computer control, at a high rate of 2 kilohertz, for example. The droplets which have been applied set during the intervals between spraying processes; this can be accomplished in various ways, for example, by spray application of a hardening medium or by supply of energy, by ultraviolet irradiation in particular. In the present case ultraviolet lamps 17 are provided in addition to the application device 9 for irradiation of the application area A with ultraviolet radiation. For the setting processes the application device 9 preferably is withdrawn along the Z axis and/or the backing element 1 is displaced by movement of the guide roller 5 along the Y axis before the corresponding elements are returned to the position selected for drop application in the following spray process.

[0019]FIGS. 4 and 5 serve to illustrate application of the process for production of adhesive fastener elements in which adhesive fastener elements 19 in the form of loops are formed on the backing element 1. In the process two stems 23 are first built up for each loop and are then bent over in arcs as illustrated in FIG. 5.

[0020]FIGS. 6 and 7 illustrate the production of adhesive closure parts with adhesive fastener elements 21 which are formed by first building up stems 23 without thickened areas on the ends. A pressure gap is formed by means of a calender roller 25, which operates in conjunction with a mating roll 27; the thickened end areas of the adhesive fastener elements 21 are formed which are trough-shaped (see FIG. 7) by calendering on the ends of the stems 23.

[0021] Liquefied acrylates the viscosity of which may be adjusted by addition as desired of a reactive thinner, for example, are suitable as plastic material to be applied in droplet form. The hardenability by means of ultraviolet radiation can be promoted preferably by addition of a photoinitiator.

[0022] In one example the plastic material contains as acrylic material 90 percent Ebecryl 4835, a prepolymer made by the UCB company, 8 percent HDDA (UCB company) as reactive thinner for viscosity adjustment, and 2 percent Darocur 1173, made by the Ciba-Geigy company, as photoinitiator.

[0023] In another example, 90-percent Ebecryl 4835 and 4-percent Ebecryl 230 from the UCB company are provided as acrylate materials. 4-percent HDDA from the UCB company is employed as reactive thinner and 2-percent Darocur from the Ciba-Geigy company as photoinitiator.

[0024] Plastic materials of a different composition may, of course, also be employed for application of the process claimed for the invention. Backing elements of a different nature, such as textile materials, or moulded elements provided for special applications may be provided in place of a sheet of polyethylene.

[0025] The invention has been described in the foregoing on the basis of examples in which the adhesive fastener elements as a whole are in the form of droplets spray-applied in succession. The process may, of course, also be applied to advantage in such a way that simply formed stems of adhesive fastener elements may, when straight stems, for example, are involved, be produced conventionally with form tools, with no additional expense, as initial material onto which droplets of the geometric configurations desired are then sprayed to produce finished adhesive fastener elements. 

1. A method for production of adhesive closure parts in which a backing element (1) is provided in at least one component area of its surface with adhesive fastener elements (3;19;21) projecting above the plane of such adhesive fastener element (1), a plastic material forming the adhesive fastener elements being applied to the backing element (1), characterized in that the adhesive fastener elements (3;19;21) are formed in at least one component area without use of a form tool, the plastic material being deposited in droplet form in succession by means of at least one application device (9).
 2. The process as claimed in claim 1, wherein the locations selected for deposit of the droplets are three-dimensional with respect to the form of the respective adhesive fastener elements (3;19;21) to be formed.
 3. The process as claimed in claim 1 or 2, wherein the application device (9) has at least one nozzle (15) and wherein the plastic material is sprayed from the nozzle (15) of the application device (9) in a drop volume of a few picoliters.
 4. The process as claimed in claim 3, wherein a liquid plastic is sprayed from the nozzle (15) as plastic material.
 5. The process as claimed in claim 3 or 4, wherein both the backing element (1) and at least one nozzle (15) are moved for three-dimensional control of the locations of deposit of the droplets.
 6. The process as claimed in one of claims 1 to 5, wherein the plastic material is solidified after deposit of each droplet or a group of droplets.
 7. The process as claimed in claim 6, wherein the solidification takes place as a result of supply of energy.
 8. The process as claimed in claim 7, wherein the supply of energy is effected by electromagnetic radiation, ultraviolet (UV) radiation or infrared (IR) radiation in particular, or by chemical reaction.
 9. The process as claimed in one of claims 6 to 8, wherein the backing element (1) and/or the application device (9) is moved for the purpose of solidification into a position which differs from the position assumed during preceding deposit of the droplet.
 10. The process as claimed in one of claims 6 to 9, wherein the plastic material possesses a controllable flexibility suitable for engagement and/or release of the adhesive fastener elements (3;19;21) after solidification.
 11. The process as claimed in claim 1 to 10, wherein the droplets are deposited at a rate higher than 50 megahertz, preferably in the kilohertz range. 